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Effects of Reduction in Windblown Sand on the Abundance of the Fringe-Toed Lizard (Uma inornata) in the Coachella Valley, California
Frederick B. Turner, Donald C. Weaver and James C. Rorabaugh
Vol. 1984, No. 2 (May 1, 1984), pp. 370-378
Stable URL: http://www.jstor.org/stable/1445193
Page Count: 9
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The habitat of Uma inornata consists solely of windblown sand deposits in the Coachella Valley, Riverside County, California. Densities of this lizard in ten 2.25-ha plots were estimated by capture-recapture analysis during the spring and summer of 1980. Six plots were arranged in pairs, with one member of each pair in apparently undisturbed habitat upwind of a tamarisk windbreak and the other member downwind of the obstruction. The other four plots were in areas with sandy hummocks or mesquite dunes. The abundance of Uma varied in different plots, ranging from as high as ∼ 45 ha-1 to zero. The three plots downwind of tamarisk windbreaks where sand depletion and surface stabilization have been underway for a number of years were essentially unoccupied by Uma. The upwind plots supported densities ranging from 11 to 45 ha-1. In general, variations in abundance of Uma were not statistically correlated with individual physical attributes of sand. By focusing on the quality of sand in dunes on the lee sides of shrubs we developed two models relating to densities of Uma. Variables of interest were: penetrability of sand in lee areas, surface coarseness, diameter of sand grains at the 75th percentile of gradation by weight, and years since surface stabilization. Both models explained about 81% of observed variation in Uma densities. Increased sand penetrability is a positive environmental factor and surface coarseness a negative one. Increasing surface stabilization is reasoned to be detrimental to Uma. Methods of capture-recapture analysis used in this study sometimes resulted in unsatifying upper bounds of confidence intervals for density estimates. Future density estimates should be derived from analyses of a chain of at least three samples.